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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/SHZYKYFVCNTR23H3GEILJGAHM5H75NYC/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "SHZYKYFVCNTR23H3GEILJGAHM5H75NYC",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/TFFUBS7YG7S2PLWRW5RK75S3MPJKDOKK/?format=api",
    "sender": {
        "address": "zleffke (a) vt.edu",
        "mailman_id": "57a24afb1cf641f98121841e6753c12e",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/57a24afb1cf641f98121841e6753c12e/emails/?format=api"
    },
    "sender_name": "Zach Leffke",
    "subject": "Re: [amsat-bb] Source for 3\" (76mm) pipe for dish mount?",
    "date": "2016-05-09T23:26:46Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/FBNIBIWNIO5WFYRSM6PLTNMD2YKJRM62/?format=api",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Hi Scott,\n\nDISCLAIMER:   Personally, I think its relevant because it has to do with \nincreasing your skill in the art of radio and satellite communications.  \nMore specifically, I think the skills needed (building/finding LNAs, \nbuilding antennas, modem development, tuning for doppler, link budgets, \netc.) are directly related to the Amateur Satellite hobby even if your \npracticing 'out of band' relative to what folks might be used to on this \nlist.  Case in point, AMSAT's nasabare.txt TLEs include spacecraft (such \nas the NOAA POES birds) that have no Amateur Radio equipment on board, \nbut they do it because people tend to have overlapping hobbies. So I'm \nposting my response to the list, but if others disagree and prefer the \nconversation be moved off list I'm more than happy to comply.\n\nI too have an interest in the GOES birds, inmarsat, and basically \nanything from airplanes (ADSB), to ships (AIS), to NWS high altitude \nballoons, to LEO birds, to MEO/HEO birds, to GEO birds. (basically \n'other' stuff that is not necessarily ham radio specific, but in the \nsame vein).\n\nSource for cheap-ish preamps/LNAS:  minicircuits.com\nBasically for LNAs, I found that minicircuits.com has a number of \n'decent' low noise amplifiers that can be used for receiving these types \nof signals.  they usually cost anywhere from 30-75 bucks (usually around \n50) depending on what you are trying to accomplish and the individual \nspecs for the band of interest, and are typically wideband enough to \ncover multiple non-contiguous chunks of spectrum (Like 1550 MHz signals \nand 1691 MHz signals in L-Band).  They also sell pretty decent (And \ncheapish, maybe $20) bandpass filters that may be of interest if you are \nin a high QRM environment.\n\nFor L-Band (Inmarsat, Iridium, etc) I made a bi-quad feed that covers \nInmarsat and the SARSAT frequencies around 1550 MHz.  I have played \naround similarly with 0.75m to 1.2m primestar type offset antennas \nmainly for the GEO birds.  The biquad plus a 0.75m offset reflector plus \nminicircuits amp plus RTL-SDR plus GNU Radio was all that was needed to \nobserve/capture recordings of the Inmarsat 'Fleet Safety Net' broadcast \nservice (an open and public service, not private communications).  \nHelicals are also good choices because they are simple to build and \ninherently wideband (forgiving of manufacturing error).\n\nMy most recent interest is in the NOAA POES SARSAT transponders (Same \nbirds that carry the 137 MHz APT transmitters).  Distress beacons \ntransmit around 406 MHz up to the birds (EPIRBs for boats, ELTs for \nPlanes, PLBs for hikers).  They rebroadcast that down at L-Band.  They \nhave a bent pipe transponder that simply rebroadcasts the beacon as well \nas a digital downlink that contains information about the beacons from \nthe onboard processing systems.  Same transmitters/data processors exist \non the GOES birds as well.  Also the system and the spec is VERY well \ndocumented and public (google COSPAS-SARSAT and look around for the \n\"technical documents\" section).  I'm trying to develop a graduate level \n(or 'really good undergraduate' level) student project (maybe in the SDR \ncourse as a class project?) to code up some open source out-of-tree \nmodules for GNU Radio to do the full demodulation/FEC decoding/data \npresentation for this.\n\nSimilarly 1690-ish MHz is an interesting band because there are three \n'targets of interest' to me.  The NOAA POES (15, 17, 18) and NOAA GOES \nbirds all transmit HRPT in this band.  Additionally, the NWS high \naltitude balloons that fly twice a day from the 50-ish (no sure about \nthe count there, but theres a lot of 'em) locations around the country \nalso operate close to this band.  So one antenna/preamp/RTL-SDR \ncombination could potentially net you access to some GEO birds, LEO \nBirds, and HABs.  (We're fortunate in Blacksburg to have an NWS station \nabout a quarter mile from my office at the airport that launches the \nballoons, others' mileage may vary on that one).\n\nFor both the NOAA balloons (more specifically Lockheed Martin - Sippican \nRadiosondes, LMS-6s) and the Inmarsat Fleet Safety Net, there are \nWindows decoders that give you free 30-day trial, then you have to pay.  \nAgain, I'm hoping to find a way to turn this into an SDR class project \n(or satcom, or summer REU program, or however I can pull it off) to have \nstudents gain experience developing modems for this.  My intent is to \ndevelop free and open source GNU Radio modules for these decoders (Train \nATCS is also on the list, but not relevant to this discussion) and then \npost them on github for others to use with GNU Radio.\n\nI'd be happy to swap notes with you (or anyone else on the list) \nconcerning these systems.  I've done a lot of legwork compiling the \nvarious sources for the specs, frequencies, etc. for these systems and \nwould be happy to send links/docs your way.  And again, even though I \nthink its relevant I could understand if others on the list don't agree \nand I'd be happy to move the conversation off list if anyone objects.\n\nHappy signal hunting!\n\n-Zach, KJ4QLP\n\nResearch Associate\nTed & Karyn Hume Center for National Security & Technology\nVirginia Polytechnic Institute & State University\nWork Phone: 540-231-4174\nCell Phone: 540-808-6305\n\nOn 5/9/2016 5:54 PM, Scott wrote:\n>>>> If you can supply photos of links of the actual dish we may be able \n>>>> to help further.\n>\n>\n> ... I found a pic online that looks right; it's a 1m Primestar dish.  \n> I cropped out just the dish - here is the link:\n>\n> https://www.dropbox.com/s/hk7dlqot0z78thb/1m-dish.jpg?dl=0\n>\n>\n> ... I have previously been using an old round DirecTV dish with \n> various home-made and purchased antennas to receive Inmarsat and a few \n> other signals but obviously needed something larger to experiment \n> further.  Both Vivaldi and patch style antennas have worked well with \n> the DirecTV dish.  I'm not completely sure what I will do with this 1 \n> meter dish, but I don't have any plans for tracking at this time.  A \n> stationary mount will be fine.\n>\n> Having already gained some familiarity with Inmarsat signals, that is \n> one option.  It may very well be beyond my reach, but I would like to \n> educate myself about what is available on the GOES-13 satellite as \n> well.  I even have a commercial FTA TV LNB to experiment with.  It \n> seems like the upcoming amateur satellites will require familiarity \n> with more gain & higher frequencies as well, so I have a lot to learn \n> there.\n>\n> LEO telemetry cubesats and the like are my main interest, but I like \n> the idea of having a dish to experiment with as well. Certainly \n> appreciate everyone's input!\n>\n> If satcom topics like Inmarsat & GOES-13 are not of interest on this \n> mailing list, by all means please feel free to contact me directly if \n> you have any pointers!\n>\n> -Scott\n>\n> ==========================\n>\n> If you are not using it in a fixed position, but for low earth orbit\n> tracking on s-band, like I am, I can give more advice. I am using a\n> 1.2 metre dish. In particular the modification for larger feeds,\n> calibration due to offset feed and real world low earth orbit tracking\n> problems.\n>\n>\n> _______________________________________________\n> Sent via [email protected]. AMSAT-NA makes this open forum available\n> to all interested persons worldwide without requiring membership. \n> Opinions expressed\n> are solely those of the author, and do not reflect the official views \n> of AMSAT-NA.\n> Not an AMSAT-NA member? Join now to support the amateur satellite \n> program!\n> Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb\n\n",
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